Higher pollinator effectiveness by specialist than generalist flower-visitors of unspecialized <Emphasis Type="Italic">Knautia arvensis</Emphasis> (Dipsacaceae) |
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Authors: | Email author" target="_blank">Magnus?LarssonEmail author |
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Institution: | (1) Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, 93106, CA, USA;(2) Charles Darwin Research Station, Santa Cruz, Galàpagos, Ecuador |
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Abstract: | Many species vary in their ecology across their geographic ranges in response to gradients in environmental conditions. Such
variation, which can influence life history traits and subsequent demography of populations, usually occurs over large spatial
scales. However, describing and understanding the causes of such variation is difficult precisely because it occurs over such
large spatial scales. In this study, we document spatial variation in the ecology of a common reef fish, Stegastes beebei, in the Galápagos Islands and test a number of potential causal mechanisms. The pattern resembles that seen in latitudinal
variation: individuals are larger, occur in higher densities, and live longer in the coldest region of the islands than those
in the warmest region. However, in this system, demography varies among regional populations separated by <150 km. Preferred
nutritious algae are more available in the cold region and comprise a greater proportion of the diet of fish in this region.
Per gram reproductive effort appears to be strongly related to temperature, despite differences in the gross magnitude and
timing of reproduction in different regions. A model of reproductive output suggests that fish in the warmest region are allocating
a greater proportion of available energy to reproduction, resulting in apparent regional life history tradeoffs. Our data
suggest that regional demographic differences in S. beebei may be driven by a combination of variation in food availability and an environmentally mediated life history tradeoff. |
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Keywords: | Latitudinal gradient Life history tradeoff Demography Galápagos Islands Reproductive output |
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